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Activating BRAF V600E Mutation in Aggressive Pediatric Langerhans Cell Histiocytosis: Demonstration by Allele-specific PCR/Direct Sequencing and Immunohistochemistry.

侵袭性小儿朗格汉斯组织细胞增生症的BRAF V600E激活突变:等位基因特异性PCR/直接测序和免疫组化表现

Méhes G,Irsai G,Bedekovics J,Beke L,Fazakas F,Rózsa T,Kiss C

Abstract

Langerhans cell histiocytosis (LCH) is a rare neoplastic disease originating from cells characterized by antigen-presenting Langerhans cell phenotype. The clinical spectrum of LCH is highly variable including localized and disseminated forms mostly occurring in children. Recently, about 60% of LCHs were reported to carry the activating BRAF mutation V600E. In our retrospective study, we evaluated the occurrence and prognostic impact of the V600E mutation in formaldehyde-fixed, paraffin-embedded samples from 15 pediatric LCH cases treated at our institution. Allele-specific polymerase chain reaction (PCR) and direct sequencing were used to demonstrate the presence of V600E mutation, and immunohistochemistry (IHC) using the mutant protein-specific VE1 antibody clone was performed to confirm mutant BRAF protein expression. Eight of 15 (53.3%) cases proved to be BRAF mutants by any of the methods applied, with a single case showing a discrepancy (PCR negative/IHC positive). Four of the BRAF-mutant cases (50.0%) showed refractory disease and progressed to death within 43 months, whereas the remaining mutant cases were stable and responded well to therapy. Wild-type BRAF cases (7/15, 46.6%) with generally comparable initial presentation were all treated successfully. In conclusion, activating V600E BRAF mutation can be frequently demonstrated in pediatric LCH by both allele-specific PCR and IHC. Unfavorable risk cases potentially also responding to BRAF-inhibitory therapy can be identified by mutation testing using archival formaldehyde-fixed, paraffin-embedded tumor samples.

摘要

 朗格汉斯组织细胞增生症(LCH)是一种起源于具有抗原递呈细胞特征细胞的罕见肿瘤。LCH的临床表现高度不一,可从原位到播散,后者多发于儿童。最近,有报道称60%的LCHs患者具有BRAF的V600E突变。

在我们的回顾性研究中,评估在本机构治疗的15例小儿LCH的福尔马林固定﹑石蜡包埋的样本中V600E突变与疾病发生及预后的关系。等位基因特异性聚合酶链反应(PCR)和直接测序检测V600E突变,免疫组化(IHC)用突变蛋白特异性VE1单克隆抗体,以便确认突变BRAF蛋白表达。

经上述方法检测15例中有8例(53.3%)显示V600E突变,其中1例突变PCR检测阴性但IHC显示阳性。在BRAF突变患者中有4例(50%)存在呼吸道病变,43个月死亡,剩余突变患者状况稳定且疗效较好。相比最初的疾病表现,野生型BRAF患者(7/15,46.6%)都治疗成功。 

 结论,在小儿LCH中等位基因特异性PCR和IHC均可检测出激活的BRAF  V600E突变。通过检测福尔马林固定﹑石蜡包埋的肿瘤样本突变情况,可以识别有潜在危险的患者,这些患者可能对BRAF抑制剂治疗有效。

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